1. Technical Field of the Invention
This invention relates to a process for making construction blocks of possible different shapes and sizes useful for various interior and exterior works such as construction of houses, buildings or walls suitable for said applications. The proposed invention is to utilise unconventional materials for the construction industry by reusing waste, e.g. from the paper industry from recycled paper or cardboard or from the wood industry, comprising cellulose fibre.
2. Description of the Related Art
In one side the outer walls of houses are conventionally built using breeze blocks laid with mortar. An additional, outer skin of bricks may then be laid with mortar. Inside the house the wall will be lined with plasterboard and then plastered to be ready to receive paint or wallpaper. The internal walls of a house will conventionally be of less substantial construction and will be lined on each side with plasterboard and plastered.
Conventionally construction blocks are made of a mixture of heavy aggregates, cement and sand, the weight gives the blocks stability and strength. These conventional blocks do not provide thermal insulation to the houses, but only are a structural element of a building.
Cellulose fibre in the form of waste paper is commonly used to produce more paper of different colour or sizes or to produce compressed card boards for various uses. Other wastes of cellulose fibre are wood shaving, sawdust and paper ash from bio-incinerators.
The United Kingdom generates 12,000,000 tonnes of waste paper and card per year and only 67% of this is recovered. 45% of the recovered waste is reutilised in England while the rest goes to foreign countries, mainly China, to be processed. The 33% not recovered still goes to landfills around the UK. This amount of waste being sent to landfill in the UK may increase in line with the instability of foreign markets and as a result of changing regulations. Research and recommendations done by WRAP (Waste & Resources Action Programme) point to a need to increase the reuse of waste in the UK to comply with the CO2 emissions reduction for the country and to be prepared for foreign market instabilities. Furthermore, the recycling of 1 tonne of paper will save 3,000 liters of drinkable water and between 3,000 and 4,000 kW of electricity, enough to supply a three bedroom house for a year. Recycling may also reduce the amount of waste going to landfill, or being incinerated with the consequent pollution to the atmosphere, and in particular CO2 emission.
There has been a technical prejudice against the use of paper and cardboard product in house walls because of fears of the risk of fire, cellulose materials generally being flammable.
Waste paper and wood waste has been used in construction in mixtures with hydraulic binders such as gypsum and cement, optionally in combination with other fillers such as sand and ash. For instance, in U.S. Pat. No. 5,350,451, a fibrous mixture of waste paper and water is formed in a blender and mixed with cement, de-watered and then formed into blocks. The dewatered slurry is moulded in forms using a hand roller to level off the top then allowed to dry by evaporation. The slurry before the dewatering step is formed of 1.8 kg of (4 lb pounds) of paper and 11.31 (3 gallons) of water, and so has a water content of more than 80%. The slurry is mixed with 0.45 kg (1 lb) of cement, but the amount of water removed before forming the block is not specified.
In U.S. Pat. No. 7,867,432 a process is described comprising the steps of mixing the shredded cellulose fibers with water, together with sodium silicate, to form a first matrix; adding cementitious material and a water dispersing super plasticizer admixture to the first matrix; adding a viscosity modifier, water reducing admixture to the cementitious containing first matrix forming a thickened second matrix; adding additional water to the thickened second matrix; forming a building product from such thickened second matrix; and allowing said building product to cure. The building product may be formed into a block for use in construction. The cellulose fibres may be derived from waste paper. The uncured product is made up of between about 70 and 74% by weight water; between about 7 and 8% by weight shredded paper; between about 18 and 20% by weight cement; and, between about 0.1 and 0.4% by weight cement conditioning admixtures and is “flopped” to entrain 4-5% air by volume. It would be desirable to avoid tile addition of sodium silicate, plasticisers and viscosity modifiers.
In U.S. Pat. No. 5,785,419 mixture from which a lightweight building material can be formed by addition of water, has the following composition by weight:
66-89% Portland type I/II cement;
0-23% fly ash; and
5.8-11.5% cellulose fibre. About 68 lb (31 kg) of dry mixture is mixed with 10 gal (38 l) water to form a pourable slurry similar to standard concrete, e.g. for forming into blocks. The cellulose fibre is in the form of a shredded “lint-like” recycled paper product. The effect of increasing the ratio of cellulose fibre to cement is explained to be the reduction in strength of the product, the increase in thermal resistance, the reduction in cost and the reduction in product block weight, within the stated ranges for the weight composition. The reduction in strength is undesirable, and seems to occur despite a high proportion of expensive cement being utilised.
In US2011/0094421 a cement premix is described formed by mixing a wet pulp of recycled paper with sand, drying the mix to a moisture level low enough that reaction with cement would not be initiated, then adding dry cement. The pre-mix may be used either by mixing with water and using as mortar or concrete or by filling into a form followed by addition of sufficient water to form green concrete, in situ. The weight ratio of recycled paper (dry) to sand to cement is 1:(20-35):(3-7). One advantage of the forming process described is the avoidance of the need to add water to the premix before filling the form, and there is no need to control the total amount of water as this is self-stabilising.
In WO2008/104772 we describe a building panel made of a hydraulic binder such as lime or cement, and various recycled components including pulverised glass, gypsum board, and waste paper or card product, in the form of fibres having length less than 5 mm. The waste paper or card is provided as a pulp and is mixed with pulverised glass and cement in a volume ratio of 7:2:1, and with water to form a mortar which is then cast into a mould. The water is added to the premixed blend of other components in a cement mixer. After the mortar is poured into a form for the panel it is said to be manually or mechanically compressed. The extent of compression is not mentioned. Several additional layers including wire mesh and for steel rods and for service trunking are added on top of the first layer as well as a surface layer of gypsum. Higher proportions of fibre pulp may be used to form lower density prefabricated sections which are then embedded in the mortar by pre-positioning in the form to produce lighter overall density panels. The panels are said to have high R values.
In US 2002/0139082 a composite building block has a light-weight core and thin fibre cement facings on each side of the core. The fibre cement is made in several steps first by dispersing cellulosic fibres, whose origin may be recycled waste paper among others, in a hydrapulper at a consistency of 1 to 6%. The product may then be partially dewatered or flash dried to a moisture content of around 5 to 50% to form individualised fibres. These are mixed as a slurry or semi-dry paste with cement, silica (sand) and water and shaped with optional post-pressing before curing. The formulation consists of hydraulic binder (cement) 10-80% by weight, preferably 25-40%, filler (e.g. sand) up to 80% by weight, preferably 45-65%, and fibre 1 to 25% by weight preferably 5-12%. The ratio of fibre to cement is relatively low.